Palladium-Catalyzed Domino-Wacker-Carbonylation Reaction for the Enantioselective Synthesis of Chromans and Benzodioxins

Abstract

A palladium-catalyzed domino reaction for the formation of chromans 9 as well as 10 and benzodioxins 13 is described starting from the alkenes 6 as well as 8 and the allyl phenyl ethers 12.The domino reaction comprises an enantioselective intramolecular Wacker oxidation, a subsequent CO-insertion and a nucleophilic substitution of the intermediately formed palladium-species.Recently we have reported on an enantioselective palladium-catalyzed domino-Wacker-Heck reaction for the total synthesis of vitamin E, 2 which not only allows the highly selective formation of the chiral chroman framework with 97% ee, but also the simultaneous introduction of a part of the side chain.Here we describe a domino process which comprises an enantioselective intramolecular Wacker oxidation, a subsequent CO-insertion and a nucleophilic substitution of the intermediately formed palladium-species.This procedure is used for the enantioselective synthesis of chromans and benzodioxins.